Cool project. You really put some planning into it. As others have mentioned S4S lumber in the US is not standardized in size. It can vary. If your using a sof

Cool project. You really put some planning into it. As others have mentioned S4S lumber in the US is not standardized in size. It can vary. If your using a softwood like Pine, it will also not be strait. This is going to cause your tight tolerances to be off. You should build this with lumber that has been fully dried, and fully straitened and taken to a lesser tolerance, something that can be plained and jointed down to.